PEPTIDE SEQUENCE DETERMINATION BY MATRIX-ASSISTED LASER-DESORPTION IONIZATION EMPLOYING A TANDEM DOUBLE FOCUSING MAGNETIC-ORTHOGONAL ACCELERATION TIME-OF-FLIGHT MASS-SPECTROMETER

This report describes the fragmentation processes for peptides induced by collisional activation of the C-12 isobar of matrix-assisted laser desorption ionization (MALDI)-generated pseudomolecular ions employin g an EBE orthogonal acceleration time-of-flight mass spectrometer and using xenon as the collision gas at a laboratory collision Energy of 8 00 eV. These MALDI-collision-induced dissociation (CID) spectra are sh own to provide sequence information of comparable quality to those obt ained by using high energy CID conditions with liquid secondary ioniza tion mass spectrometry on a four-sector tandem instrument. Peptide seq uencing via MALDI-CID is demonstrated on three tryptic peptides obtain ed from a bacterial protein (P450 isozyme) of unknown sequence. Sensit ivity is shown to be at the 1 pmol level for standard peptides.